The present invention relates to medical diagnostic equipment, and, more particularly, to apparatuses for supporting and positioning x-ray and other medical imaging devices.
Angiography involves the use of x-rays or other electromagnetic waves to examine arteries, veins, organs, and the like. Typically, a contrast agent (e.g., x-ray dye) is applied to the features under observation, via a catheter passing through the skin or an injection, to differentiate them from surrounding regions of the body. For most angiographic procedures, the x-rays being applied to a patient must be precisely directed, in order to ensure that the proper area is examined. Since orienting patients with respect to stationary x-ray devices (which typically include an x-ray source and an x-ray receptor) has been found to be imprecise, many gantry-like mechanisms have been developed over the years for supporting and positioning x-ray devices.
In designing x-ray support apparatuses, the x-ray device should ideally be positionable for use anywhere around the periphery of a patient in three dimensions. More specifically, it is typically desirable to utilize spherical angulation, where x-rays can be directed from any loci on an imaginary sphere centered on the patient to an isocenter of the x-ray device (the isocenter is the point of intersection of an axis defined by the x-ray source and receptor and the axis of angulation, i.e., the axis of device rotation). Other factors to take into account include: maintaining the x-ray beam normal to the x-ray receptor; the size of the examination room, and the room""s ability to accommodate large devices; unrestricted access to the patient, especially around the head area; minimizing control complexity and/or the need for computer image correction or manipulation; and, as always, cost.
Most current x-ray device support apparatuses utilize either a parallelogram-shaped construct or a combination of C-, U-, and/or L-shaped arms for x-ray device positioning and (ideally) spherical angulation. An example of the former is shown in U.S. Pat. No. 3,892,967 to Grady et al. (xe2x80x9cGradyxe2x80x9d). In Grady, an x-ray source 23 and receptor 22 are positioned with respect to a patient P by way of an angularly-adjustable, pivoting, rotating parallelogram 3, 5, 8, 9. This achieves 360xc2x0 rotation coverage about the patient P, by virtue of the parallelogram being rotatable about shaft 2, and 55xc2x0 of head/foot tilt (the arms 8, 9 can be moved in and out). Thus, the device basically moves in an unrestricted way on the surface of a sphere about the patient, and the x-ray image itself inherently always remains xe2x80x9cuprightxe2x80x9d irrespective of the compound angles used. However, to cover from head to foot on a six feet tall patient, the xe2x80x9cthroat depthxe2x80x9d (clearance) of the support apparatus has to be over six feet. This makes the support apparatus at least ten to twelve feet long, plus the patient tabletop has to travel at least six feet, which means it must be eight to nine feet long. Thus, the entire system is almost twenty feet long, necessitating a twenty-eight or thirty foot long room, which might cause architectural problems.
Because parallelogram-based devices are so bulky, various C-arm based devices have been developed over the years. However, large C-arms arc difficult to balance (a parallelogram can be an entirely mechanically-balanced device), since the entire mass of the C-shaped structure is offset to one side. Accordingly, these have primarily taken the form of a simple, light, balanced, C-shaped arm which holds the x-ray source at one end and the receptor at the other end. The C-shaped arm slides in a journal, and is positionable by way of one or more pivoting arms attached to the journal. Such devices can deliver most of the angular coverage of a parallelogram in a smaller space, but typically have several severe, inherent problems, such as the inability to carry heavy equipment without dangerous power-driven operation.
Furthermore, with existing C-arm based devices, as the axis of the x-ray beam approaches the horizontal, rotating the horizontal axis only serves to rotate the image, without changing the viewing angle. This results in zero image rotation with a vertical beam, and 100 percent rotation (only) at a horizontal beam. In between 0xc2x0 and 90xc2x0 the x-ray beam/positioner angular relationship is complex, and the two rotation axes interact. The result is a tilted image as viewed on the x-ray image screen. This effect can be compensated for by either mechanically rotating the x-ray receptor (and also the source collimator if a square x-ray field is utilized) according to a pre-programmed code, or by implementing an xe2x80x9cimage de-rotationxe2x80x9d scheme where the image, as stored electronically, is manipulated by digital means. However, such systems are expensive, and can ultimately degrade the image.
There have been numerous variations in the design and construction of C-arm based x-ray gantries, but two main divisions are apparent: types where the horizontal C-arm axle comes at the patient from the left side, and types where the C-arm axle comes over the patient""s head. In regards to the former, the achieved angle and tilting image problem is severe, plus the left side of the patient is obstructed. To solve that, putting the C-arm axle at the head of the patient gives good angular coverage, but the patient can only be imaged as far as the abdomen area, since otherwise the patient""s head will hit the C-arm structure. The C-arm cannot be made larger in radius, as the center of rotation must be in the patient (isocentric operation is a requirement), and the floor and ceiling set bounds on the outer diameter of the C-arm, when the center of rotation is in the patient""s body. Thus, xe2x80x9chead endxe2x80x9d mounting brings restricted coverage of the patient""s length, especially below the abdomen.
U.S. Pat. No. 4,358,856 to Stivender et al. (xe2x80x9cStivenderxe2x80x9d), with reference to its FIG. 2, attempted to solve these problems by mounting a sliding, journal type C-arm 25 (with rotating axle construction) on a rotating, swinging, L-shaped member 10, where the lower right part of the xe2x80x9cL,xe2x80x9d viewed as an alphabetical character, is attached to a bearing 14 centered under the isocenter 37. While this design provided good angular coverage, it presented its own problems. More specifically, the height or structural width of the horizontal member of the L-shaped arm 10 on the floor 15 effectively xe2x80x9craised the floor,xe2x80x9d requiring that the C-arm 25 have a smaller radius by about six inches. This is a critical shortcoming, as everything is much closer to the table and patient, due to the smaller xe2x80x9cCxe2x80x9d radius. Furthermore, swinging the L-shaped arm 10: (i) rotates the image yet again on another axis (now a three way interaction); and (ii) is problematic in a clinical sense, as it sweeps out a 90xc2x0 arc to the left of the patient""s head, where various monitors would normally be placed, medical lines are attached to the patient, and where nurses typically stand. As a result, units such as those shown in Stivender are almost always left at the head end of the patient (i.e., the L-shaped arm is not moved), mimicking other existing devices where a large radius C- or U-shaped arm is permanently mounted at the head.
U.S. Pat. No. 4,653,083 to Rossi (xe2x80x9cRossixe2x80x9d), with reference to its FIG. 1, discloses a C-arm based x-ray gantry with: a floor-mounted stand 1; an outer C-shaped track 8 attached to the stand; and an inner U-shaped arm 11 rotatably connected to a carriage 9 that slides along the outer track 8. While this device provides good angular coverage, it is very difficult to balance, and, therefore, was never commercially produced. More specifically, because the outer track 8, inner arm 11, and table T are all offset to one side of the stand 1, the stand has to be either provided with a large counterweight for balance, or the stand has to be particularly well secured to the floor. Furthermore, to balance the x-ray source X and receptor I, a counterweight (not shown) was required to be disposed in the vertical portion of the inner arm 11. This placed a large weight far off the x-ray beam axis and far from the isocenter C, leaving the whole inner arm 11 severely unbalanced with respect to the outer track and stand. Also, while the inner arm 11 was balanced about its pivot rotation axis 12, it required a large motor to crawl around the outer track 8.
Another problem associated with Rossi and similar designs is that they utilize cameras and image intensifier x-ray tubes (e.g., intensifier I in FIG. 1 in Rossi), resulting in a very tall and heavy assembly. Also, there is the possibility of the top of the image tube interfering with the outer C-arm or track when the image tube is moved axially away from the x-ray tube. Accordingly, the outer track must be quite large to accommodate the twelve- to sixteen-inch image intensifier tube, and still allow the inner C- or U-shaped arm to swing freely to compound angles without hitting the outer track.
Accordingly, it is a primary object of the present invention to provide a floor-mounted x-ray device support and positioning apparatus that achieves full spherical angulation, without image rotation, via xc2x190xc2x0 transverse coverage across or around the patient""s long axis.
Another primary object of the present invention is to provide an x-ray support apparatus that can be positioned to minimally interfere with clinical use patterns, including leaving the head end of a patient completely clear, for all projections of interest.
Another object of the present invention is to provide an x-ray support apparatus that is inherently stable, that can fit inside a normal-sized hospital room, and that does not require the installation of support buttresses or the like.
Still another object of the present invention is to provide an x-ray support apparatus that utilizes a flat panel x-ray receptor (thereby eliminating the need for an image intensifier lube), and that utilizes an improved counterweight system for properly balancing the flat panel receptor against a heavier x-ray source.
A dual C-arm angiographic device for flat panel x-ray receptor (xe2x80x9cdual C-arm gantryxe2x80x9d) comprises: a base attached to the floor; an outer C-shaped track non-movably attached to the base; a crawler carriage that moves along the outer track; and an inner C-shaped instrument bracket (xe2x80x9cinner C-armxe2x80x9d), concentric with respect to the outer track, that is pivotally or rotatably attached (xc2x1180xc2x0) to the crawler carriage ((he inner C-arm is only rotatably attached to the crawler carriage, and does not slide within or with respect to the crawler carriage). A detector/counterweight housing and a flat-panel x-ray receptor, as well as an x-ray tube and collimator, are respectively attached to the ends of the inner C-arm. Also, the bottom end of the outer track terminates at the base, such that the outer track arches over a separate patient support table.
For positioning the inner C-arm, the crawler carriage (and hence the inner C-arm) can be moved xc2x190xc2x0 by traversing from one end of the outer track to the other. However, the inner C-arm pivot point (the point on the crawler carriage at which the inner C-arm is pivotally connected) is circumferentially offset from the point at which the crawler carriage is movably attached to the outer track. This effectively allows the crawler carriage to xe2x80x9cstick outxe2x80x9d past the bottom end of the outer track, resulting in full spherical angulation and providing a full range of clinical positioning, while still allowing for the outer track to be xe2x80x9carched upxe2x80x9d over the table. In other words, the circumferential offset allows the outer track to be placed where it interferes the least with clinical use patterns (specifically, on the side of a patient, away from the head).
The base may be provided with a linear bearing or roller track, slidably connected to a floor plate or carriage. This allows the base to be moved, e.g., towards or away from the patient support table
For the dual C-arm gantry to work properly, the top and bottom of the inner C-arm must weigh approximately the same to balance it around the pivot point. Accordingly, a counterweight system is housed in the detector/counterweight housing. The counterweight system is used to provide a balancing weight to the x-ray source tube and collimator, which is typically much heavier than the flat-panel x-ray receptor, and to provide a balance for the receptor panel itself, which can be moved in and out (to bring it closer or further away from a patient).
The dual C-arm gantry can also be used for supporting and positioning other medical imaging or radiologic devices.